Abrasive article



May 14, 1963 w. E. cowLEY 3,089,294

ABRASIVE ARTICLE Filed Dec. 23, 1959 2 Sheets-Sheet 1 May 14, 1963 w. E. cowLEy 3,089,294

ABRASIVE ARTICLE Filed Dec. 23, 1959 2 Sheets-Sheet 2 3,089,294 Patented May 14, 1963 3,089,294 ABRASIVE ARTICLE William E. Cowley, Louisville, Ky., assignor to Vermont American Corporation, a corporation of Kentucky Filed Dec. 23, 1959, Ser. No. 861,575 Claims. (Cl. 51--186) This invention relates to a new and improved abrasive article `adapted for manual or machine use and suitable for removal of stock and for surface nishing of a wide variety of materials such, for example, as Wood, plastic, cement and even metals.

Heretofore it has been common to employ sheets of paper, or sometimes cloth, to which has been glued grit material in the form of grains or particles of sand, aluminum oxide, metal carbides, diamonds and the like. The grit material comes in various sizes and is distributed in various densities upon the sheets. However, such sheet material, particularly when formed of paper, has had a short life because of its lack of strength and tendency to tear or crack. Also the grit material has a tendency to become loosened after a short Working period.

While the foregoing disadvantages of prior abrasive articles may have been mainly an inconvenience for hobbyists and home workshop use, they have been an expensive addition to the cost of production in industrial operations, not merely because of the short life of the abrasive article but even more so because of the down time" of the machines employing them, and the cost of labor in frequently replacing the articles.

Accordingly, it is an object of my invention to provide a more durable abrasive article which, though more expensive in initial cost than sandpaper, for example, has a life many times that of sandpaper and which has superior abrasive action, thereby making it a superior product and less expensive in the long run.

It is a further object to provide such an improved sheet-like abrasive article which lends itself not only to manual but also machine use and whether carried by a solid support, such as a manually operated sanding block where atness of the article must be maintained, or by a resilient support, such as the rubber disk of a rotary sander where flexibility of the article is necessary, or by other means.

To the foregoing ends I provide, in its preferred form, a thin sheet-steel base member to one side of which is brazed by a conventional brazing process, particles of fragmented tungsten carbide of s-elected size, and to the other side of which is secured a thin spring-steel backing member. While the backing member may be secured to the base member in more than one way, I prefer to bend at least a portion of the margin of the base member back and over the backing member. In that way I can assure that the abrasive work surface will retain its generally flat configuration and yet have ya resilience when required. Also, damage to the edge of the base member, as by denting or other deforming acts, is largely prevented. The latter is important, since denting of an edge of the base member produces a raised point or line which is work hardened and gouges the surface which is being finished. It is difficult if not impossible to return the abrasive surface to its original condition after such denting and therefore it is an important object of my invention to prevent it.

Other objects, advantages and modifications of my invention will become apparent or be obvious from a consideration of the following description when taken in conjunction with the appended drawings in which:

FIGURE 1 is a perspective view of an abrasive article in the form of a sanding block;

FIGURE 2 is a fragmentary sectional view on the line 2-2 of FIGURE l looking in the direction of the arrows;

FIGURE 3 is a fragmentary sectional view on the line 3-3 of FIGURE l looking in the direction of the arrows;

FIGURE 4 is a top plan view of a blank which is used to construct the base member of the abrasive article of FIGURES l to 3;

FIGURE 5 is a plan view of an unmounted abrasive article in the form of yan abrasive disk for a rotary sander;

FIGURE 6 is a side elevation on greatly reduced scale of an article such as that of FIGURE 5 mounted on a resilient support and showing the article in a typical working condition wherein it is flexed from its normal at plane;

FIGURE 7 is a sectional view on the line 7-7 of FIGURE 5;

FIGURE 8 is a perspective view of an abrasive sheet adapted for use with a sanding block and having a portion broken away to show the modified structure.

Turning then to FIGURES l. 2 and 3, there will be seen a sanding block 10 having a support means 11 comprising an upper hand-grip portion, which may be made of wood or plastic or other suitable material, and a flat under surface 12. The hand-grip portion provides a ready means for manually gripping and manipulating the sanding block, and the under surface 12 provides a hat rigid backing support. The felt pad 13, having an outline commensurate with that of the under surface 12 of block 11 and of generally uniform thickness throughout, may be glued or otherwise secured to the under surface 12 of block 11 to provide a cushioning effect. Disposed on the outer side of the felt pad 13 is a thin abrasive article indicated generally by the reference numeral 14.

The abrasive article 14 is generally sheet-like and of a rectangular shape, though other shapes are usable. It has a width corresponding substantially to the Width of the hand-grip portion 11 and a length somewhat greater than portion 11, so that its ends 15 may be bent up and then back into engagement with the ends of block 10, and may be staplcd to the block by staples 16, or otherwise secured. As can be best seen from FIGURES 2 and 3, the abrasive article 14 comprises a relatively thin base member 17 forme-d of sheet material, `and has a hard abrasive grit material 18 secured to its outer flat side. A relatively thin resilient backing member 19, also formed of sheet material, is secured to the base member, and is disposed between the base member and the felt pad 13.

The base member is preferably a steel sheet having a thickness in the approximate range of .002 to .010 inch, and the backing member is preferably of spring steel having a thickness in the approximate range of .003 to .010 inch. It will be appreciated that in the drawings the thicknesses of the sheets cannot be accurately portrayed.

Preferably, the abrasive grit material is fragmented particles of tungsten carbide and they are brazed to the base member by known copper brazing materials such as the appropriate materials disclosed in Klinker Patent No. 2,606,132 or other materials. It will be appreciated that other abrasive grit material may be employed and in varying sizes, and that other than steel sheets may be used for the base member, and that other than spring steel backing members may be employed. However, the materials specified as preferable have been found very satisfactory in use.

The abrasive particles 18 are secured in a single layer thickness to the base member 14 except at its ends 15 and side margins 2.1 which are bent over the backing member 19. Only enough brazing material is employed as will cause the particles to be strongly secured to the base member. It is found in manufacture of the product that the brazing material tends to run to the particles and to provide a fillet of brazing material between the base member and the sides of the particles, as well as a bond to the under surface of the particles. Depending upon the shape of a particle and the amount of brazing material used, the fillet may extend as much as halfway up the side of the particle. Usually there is not an appreciable amount of brazing material in the blank spaces between the particles, because none is needed there. Preferably, the particles are distributed on the base member in such spaced relation as to avoid clogging when the abrasive article is used, and the particles may be distributed at random rather than in a particular spaced pattern.

Prior to association of the base member `17 with the resilient backing member 19, the base member takes the form shown in FIGURE 4. The dotted lines along the longer sides in FIGURE 4 represent the lines along which the marginal portions 21 of the base 17 are bent upwardly. Then the resilient backing member is inserted between the bent-up sides and the marginal portions 21 are thereafter bent down over the resilient backing mem ber 17 to grip the latter in place. In bending over the marginal portion 21, care is taken not to produce a sharp crease in the metal. Prior to associating the base member 17 and backing member 19, a resilient adhesive or cement may be employed between the two members, if desired, after which the margins 21 are bent over to grip the backing member 19.

The resilient backing member 19 is of such length that it is shorter than the base member 17 by an amount approximately that corresponding to the bent-up end portions 15. In other Words, the bend-line for the end portions 15 is at the end of the backing member or just adjacent the end. However, it will be observed that the bent-over side margins 21 of the base member 17 extend beyond either end of the backing member `19, and, therefore, the ends of the bent-up margins 21 form a part of the bent-up end portions 15 of base member 17. That results in sturdy corners, which are not then easily dented or bent in usage. In this way, the entire abrasive article 14 is strengthened, while yet remaining at and flexible, and damage to the margins or corners is substantially eliminated. In articles of this type which have been made heretofore, the side margin and corners have been very vulnerable, with the result that when once dented or otherwise distorted, the distortion results in a certain work hardening of the sheet, and it is never possible to get the sheet truly flat again. The result of that is that there are certain high points or ridges which gouge or scratch the surface on which work is being performed.

In an abrasive article approximately six inches long and 2% inches wide, such as that shown in FIGURES l to 3, the bent-over margins 21 may overlap the resilient backing sheet by approximately 1/13 to 1/8 inch. However, other proportions may be employed as well as other shapes.

As an example of another shape which the abrasive article may take, reference may be made to FIGURES 5, 6 and 7 wherein the base member 17A is circular in outline and has as its marginal portion 21A bent over and into holding engagement with the entire periphery and margin of the resilient backing member 19A. On the outer face of the base member 17A is secured abrasive grit material 18A, as described above with respect to FIGURES l through 4. The base member and backing member are both tapered at their central portions, as well as apertured and cross-slotted, as shown at 22, and the cross slots in each are aligned. The tapered center portions, apertures and slots accommodate the abrasive disk to a resilient type of rubber backing disk 23, such as is used in connection with motor driven sanding machines of the type shown at 24 in FIGURE 6. FIGURE 6 also illustrates how the abrasive disk may be flexed in use. While there is a certain resilience in the base member 17A, in order for the abrasive disk to retain a generally flat condition the spring steel backing member 19A is employed. The abrasive grit material 18A preferably is distributed over the greater part of the surface of the base member 17A, but not on the periphery nor on the bent-back marginal portions 21A, nor on the center tapered portion at 22.

In FIGURE 8 there is illustrated a modification 14B of the abrasive article 14. If the base member 14B has certain characteristics, it may be possible in some circumstances to dispense with the resilient backing member and to rely upon the bent-over marginal portion 21B to protect the side margin against denting and other deformation, and to prevent damage to the corners. However, the preferred structure is that shown in FIGURES 1 through 3.

While I have illustrated preferred forms of my invention, I do not intend to be limited thereto, except insofar as the claims are so limited, since certain modifications coming within the scope of the invention will be suggested to those skilled in the art, particularly in the light of my disclosure.

I claim:

1. An abrasive article of manufacture comprising a base member formed of a thin sheet of relatively soft steel having bent-up end portions adapted to be secured to a supporting structure, said base member having a work surface to which is brazed tungsten carbide grit material, a resilient sheet-steel backing member extending between said end portions on the other side of said base member behind said grit bearing work surface, and marginal side portions of said base member being bent back upon themselves, at least in the areas of the bend lines of the bent-up end portions to strengthen the corners and to secure said backing member to the base member.

2. An abrasive article of manufacture comprising a rectangular base member formed of a thin sheet of steel to one side of which is secured by brazing, except at its end and side margins, an abrasive grit of tungsten carbide, a thin spring steel backing member secured to the other side of said base member by said side margins being bent over the side margins of the backing member and with said backing member extending along said other side a distance short of both ends of the base member, and with the end margins of the base member being bent up and away from the grit-bearing side of the base member beyond the ends of said backing member, said bent over margins of said base member extending into the bent back area of the end margins.

3. An abrasive article comprising support means having an upper hand grip portion and a flat under surface of rectangular configuration, cushioning means of substantially uniform thickness secured to said under surface and commensurate with it in outline, a base member formed of a thin sheet of metal having a thickness of the range of .0-02 to .010 inch and generally rectangular in plan and with its side margins bent back upon one side of the base member but without producing a sharp crease at the bend line, hard abrasive grit material secured to the other side of said base member, said base member underlying the cushioning means with its grit bearing side exposed and having its opposite ends, including portions of the bent back side margins, bent away from the grit bearing side and stapled to said support means.

4. The article of claim 3, including a resilient metal backing member secured to the base member by the bent back side margins of said base member, said backing member having its ends terminating short of the bend lines of the base member.

5. An abrasive article of manufacture comprising a relatively thin member formed of sheet material on one side of which is secured hard abrasive grit material and providing a generally planar working surface on said one side, said sheet material being normally non-stretchable but being subject upon sufficient impact or bending to become permanently deformed out of the plane of the working surface, and said thin member having a marginal portion exposed during usage of such possible deformation of the working surface, means associated with said marginal portion adapted to protect against permanent deformation comprising a portion of the margin bent back upon itself, and a relatively thin resilient backing member formed of sheet material more resilient than said resilient member and secured to said thin resilient member by marginal portions of the thin resilient member bent back upon said backing member to grip the same, the thin resilient member being a resilient high-carbon steel sheet having a thickness `in the approximate range of .002

to .010 inch and the backing member being of spring steel having a thickness in the approximate range of .003 to .010 inch.

References Cited in the le of this patent UNITED STATES PATENTS 2,298,318 Stratford Oct. 13, 1942 2,569,253 Opland Sept. 25, 1951 10 2,906,612 Anthony et al Sept. 29, 1959 FOREIGN PATENTS 385,649 France Dec. 27, 1907 

1. AN ABRASIVE ARTICLE OF MANUFACTURE COMPRISING A BASE MEMBER FORMED OF A THIN SHEET OF RELATIVELY SOFT STEEL HAVING BENT-UP END PORTIONS ADAPTED TO BE SECURED TO A SUPPORTING STRUCTURE, SAID BASE MEMBER HAVING A WORK SURFACE TO WHICH IS BRAZED TUNGSTEN CARBIDE GRIT MATERIAL, A RESILIENT SHEET-STEEL BACKING MEMBER EXTENDING BETWEEN 